In geology, a “dip” refers to the magnitude and azimuth of inclination of a plane relative to a horizontal plane. The dips of bedding planes within a section of the formation define a dip pattern or trend. Such dip patterns or trends are useful in geological interpretations, which are in turn very important in the petroleum industry for a proper understanding of the properties and characteristics of the various oil and gas reservoirs and for accurate modeling and simulating of the reservoirs.
The dip trends in a subsurface formation are interpreted largely based on borehole geological (dipmeter and image) log data. A number of advanced devices and sensors have been developed to facilitate the acquisition of such borehole geological log data. Oil-based mud imagers (OBMI™), fullbore formation micro imagers (FMI™), and other advanced devices can provide fast and high-resolution images of the borehole and/or measurements to compute dips. These borehole geological devices make it possible to perform geological, structural, and stratigraphic interpretations, including thin-bed detection, compartmentalization delineation, high-resolution net-pay calculations and well correlations.
In addition, the inventors of the present invention have co-invented a patented rock classification system called iCore™. The iCore™ rock classification system, available from Schlumberger Oilfield Services, Inc., uses a Ternary Diagram model and a set of classification rules to classify the rock data obtained from a borehole spectroscopy tool. Borehole spectroscopy tools provide data to compute total dry weight percentages of the QFM (quartz, feldspar, and mica), clay, carbonate, pyrite, siderite, anhydrite, coal, and salt in the formation. Based on the set of rules, the iCore™ system determines whether the rock data represents marl, claystone, shale, sandy shale, shaly sand, sand, clean sand, calcareous sand, calcareous shale, carbonate, sandy carbonate, or shaly carbonates. Such a rock classification system has greatly helped improve geological interpretations. For more information regarding the iCore™ rock classification system, the reader is referred to commonly assigned U.S. Pat. No. 6,751,557, entitled “Rock Classification Method and Apparatus,” issued on Jun. 15, 2004, and incorporated herein by reference in its entirety.
While the above tools are useful and provide very accurate data regarding the borehole geology, the dip trend recognition and interpretation process has heretofore remained a largely manual process. This process generally calls for geoscientists and interpreters to manually examine (i.e., view) the borehole geological log data, identify the individual dips, study the dip trends, and make a geological interpretation. Such a process, however, requires an exceedingly large amount of time when thousands of feet of borehole image log data are involved, as is often the case in the petroleum industry. Accordingly, what is needed is a way to automate the dip trend interpretation process as much as possible in order to reduce the amount of time required by geoscientists and interpreters.